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Topics
Software Process
Software Lifecycle
Software Process Models

Software Process Models
A software process model is a simplified representation of a software process. Each process model represents a process from a particular perspective (viewpoint), and thus provides only partial information about that process. Each process model follows a particular life cycle in order to ensure success in process of software development.
The most popular process models are:
1. The waterfall model: This takes the fundamental process activities of specification, development, validation, and evolution and represents them as separate process phases such as requirements specification, software design, implementation, testing, and so on.
2. Incremental development: This approach interleaves the activities of specification, development, and validation. The system is developed as a series of versions (increments), with each version adding functionality to the previous version.
3. Reuse-oriented software engineering: This approach is based on the existence of a significant number of reusable components. The system development process focuses on integrating these components into a system rather than developing them from scratch

The waterfall model:
One such approach/process used in Software Development is "The Waterfall Model". Waterfall approach was first Process Model to be introduced and followed widely in Software Engineering to ensure success of the project. In "The Waterfall" approach, the whole process of software development is divided into separate process phases, these are:
Requirements analysis and definition: The system’s services, constraints, and goals are established by consultation with system users.

System and software design: The system design process allocates the requirements to either hardware or software system by establishing an overall system architecture. The software design involves identifying and describing the fundamental software system concepts and their relationships.
Implementation and unit testing: Implementation means the software design is accomplished as a set of programs or program units. Unit testing involves verifying that each unit meets its specification.
Integration and system testing: The individual program units or programs are integrated and tested as a complete system to ensure that the software requirements have been met. After testing, the software system is delivered to the customer.
Operation and maintenance: This is the longest life cycle phase. The system is installed and put into practical use. Maintenance involves correcting errors which were not discovered in earlier stages of the life cycle, improving the implementation of system units and enhancing the system’s services as new requirements are discovered.